Hydraulic control for internal combustion engines, in particular for gas engines



F. FIEDLER PARTICULAR FOR GAS ENGINES Filed March L7, 1964 HYDRAULIC CONTROL FOR INTERNAL COMBUSTION ENGINE June 28, 1966 IT: vevziofi Franz Fieizel- United States Patent 3,257,999 HYDRAULIC CONTROL FOR INTERNAL COM- BUSTION ENGINES, IN PARTICULAR FOR GAS ENGINES Franz Fiedler, Graz, Austria, assignor to Hans List, Graz, Austria Filed Mar. 17, 1%4, Ser. No. 352,448 Claims priority, application Austria, Mar. 22, 1963, A 2,287/63 1 Claim. (Cl. 123-90) The invention relates to a hydraulic control for internal combustion engines, in particular for gas engines, comprising a control pump driven by the internal combustion engine, the individual elements of said pump being fed from a control liquid reservoir and producing intermittent feed pulses, each of them communicating via a delivery pipe and a check valve with a jack, the Working piston of which controls the opening and closing motions of a spring-loaded injection-gas valve, the said jack being connected with the control liquid return pipe via a drain discharging on one side, during the initial stage of the valve closing motion, and, after the discharge pipe or drain has been closed by the working piston, via a by-pass pipe comprising a throttle and discharging into the delivery pipe, duriug the final stage of the valve closing motion.

In conventional controls of this type a fuel injection pump of a conventional design serves as a control pump, the surge chambers of the individual pump elements communicating directly with the delivery pipe, the control liquid return pipe discharging into said delivery pipe before the latter enters the check valve so as to assure an intermittent and alternating flow of the control liquid through the delivery pipe in both directions. For the purpose of feeding the individual pump elements, the control liquid is removed from a high-level reservoir and delivered by means of a special feed pump via a delivery pipe and a check valve to the above-mentioned by-pass pipe from where it passes via the return pipe and the delivery pipe into the surge chamber of the pump element. During the following working stroke of the pump piston, the control liquid is delivered through the delivery pipe in opposite direction to the jack, the piston of which opens the injection-gas valve of the internal combustion engine. During the return stroke of the piston of the injection pump the control liquid flows from the jack through the return pipe and/or -by-pass pipe and through the delivery pipe back to the pump element and returns via its suction bore into the control liquid circuit.

Valve actuating devices of this type present a number of drawbacks in connection with the closing motion of the valves. If the valves operate at high speed, compressional vibrations are liable to occur in the control liquid, said vibrations being transmitted to individual valves, thereby causing damage to the valve seats. These presure fluctuations are the result of sudden deliveries of control liquid as are increasingly liable to occur with rising speeds, so that in order to assure smooth closing operations, it is necessary to restrict the maximum speed of internal combustion engines to approximately 600 rpm.

In addition to these shortcomings, conventional controls require additional pipings and are of a relatively complicated design so that it is doubtful whether the advantages of such a hydraulic control justify the high manufacturing cost, apart from the greater susceptibility to trouble of similar appliances.

The invention eliminates the above-mentioned shortcomings and has for its object the provision of a greatly simplified control ensuring smooth operation even at considerably greater operational speeds than has hitherto been Patented June 28, 1966 "ice possible. According to the invention, this is achieved by providing each pump element on the delivery side of the pump with a relief valve and by arranging a differential piston valve between the delivery pipe and the jack in addition to the check valve and in parallel relation to same for the purpose of controlling the return of the control liquid to the return pipe discharging directly into the control liquid reservoir, the major diameter piston front surface of the differential piston valve being subject to the intermittent delivery pulses of the control pump, whereas the minor diameter piston front surface, designed as a return valve is impinged upon by the control liquid flowing back from the jack, the effect of the provision of a relief valve for the injection pump being a momentary relief of pressure of the delivery pipe and of the working piston, and at the same time of the differential piston valve, thereby directly initiating the valve closing operation. This offers the advantage of short valve open ing periods even at high speeds up to approximately 1800 r.p.m., so that valve overlap between the blowing and scavenging operations is definitely avoided. Moreover, this design offers the advantage that any standard-type fuel injection pump of the kind used in conjunction with Diesel engines is suitable for incorporation in the control according to the invention without any alteration in design, provided the elements of the said fuel injection pumps are equipped with relief valves. Consequently, the extra cost'involved in the design and construction of a special pump can be saved.

Another substantial advantage is derived from the fact that the control liquid flowing back during the valve closing motion passes directly via the diiferential piston valve into the pressureless return pipe, the comparatively insignificant resistance to flow to be overcome permitting a reduction of the valve closing force and consequently, a diminution of Wear of the valve seat.

Smooth operation of the device even at high speed ranges is mainly assured by the closed control liquid circuit, since in contrast to the conventional device no reversal of the flow of control liquid occurs in the delivery pipe, thereby precluding the risk of vibrations during the valve closing motion as is the usual result of such reversals.

The fact that the eifect according to the invention is achieved at considerably less constructional expenditure is particularly important as it ensures inexpensive and trouble-free operation of the system. For example, a single delivery pipe serves to feed each jack, whereas for the return of the control liquid to the reservoir a common pressureless manifold is provided. Since according to the invention, a special high-level reservoir is not required for the storage of the control liquid, the reservoir is easily accommodated in conventional internal combustion engines where the available space is generally restricted. Although the temperature of the control liquid is liable to rise quickly, particularly if high speeds prevail, special cooling appliances for the control liquid can be normally dispensed with in view of the Well regulated cooling circuit, since in general, the cooling effect of the reservoir fully compensates the rise of the control liquid temperature in actual operation.

A further superiority of the control according to the invention over conventional controls resides in its permanent readiness for use, since the control piping system is automatically vented during operations. Only for the initial start of the control is it necessary to provide for the venting of the control piping system by means of a single venting screw at the topmost point of the piping system.

Further details of the invention will appear from the following description with reference to the accompanying drawing in which the one and only figure shows an embodiment of the invention.

For each of its pump elements the control pump 1 comprises a relief valve 1' on its delivery side, to which a delivery pipe 2 is connected. At the other end, the delivery pipe 2 forms two branches, one of which communicates via a return valve 3 and an additional delivery pipe 4 with the surge chamber of a jack 5, whereas the other branch of the delivery pipe 2 discharges into the surge chamber of a differential piston valve 14 closed by the piston front surface 16. Slideably arranged inside the jack 5 is a working piston 6, the free extremity of which rests on the stem end surface of an injection-gas valve 7 loaded by a valve spring 8 in closing direction. The surge chamber of the jack 5 communicates via a lateral bore 10 with the differential piston valve through the discharge pipe 9 discharging on the side of the piston front surface 18 designed as a return valve which thus separates the discharge pipe 9 from the overflow chamber 19 of the differential piston valve 14. The overflow chamber 19 presents a lateral opening for the return pipe 13 discharging directly into the control liquid reservoir 15. The control liquid circuit is closed via suction pipe 20 connecting the control liquid reservoir 15 with the control pump 1. Between the jack 5 and the differential piston valve 14 a by-pass pipe 11 is provided in addition to the discharge pipe 9, said by-pass pipe communicating with the delivery pipe 4 on one side and with the discharge pipe 9 on the other side and comprising a throttle 12.

The operation of the control according to the invention is as follows:

The delivery pulse produced by the control pump 1 opens the check valve 3 via a relief valve 1' and a delivery pipe 2. The control liquid acts via a delivery pipe 4 on the working piston 6 which opens the injection-gas valve 7 against the action of a valve spring 8. The same delivery pulse also impinges upon the larger piston front surface 16 of a differential piston valve 14, thereby pressing the piston front surface 18 designed as a return valve in closing direction against its seat. pipe 9 is separated from the overflow chamber 19 of the differential piston valve 14 so that the control liquid is prevented from flowing back into the return pipe 13 during the delivery stage causing the valve to open. Upon completion of the delivery operation by closing the suction bore 21 of the injection pump 1 by means of the pump piston 22 in the same way as with Diesel injection pumps, the delivery pipe 2 is relieved of pressure by means of the relief valve 1 located in the injection pump 1, the check valve 3 closing and separating the control pipe system consisting of the surge chamber of the jack 5 and the pipes 4, 9 and 11 from the delivery pipe 2 and/or the control pump 1. Then the valve. spring 8 closes the injection-gas valve 7, pushing the Working piston 6 back and pressing the control fluid through the bore 10 and the drain 9 against the small piston front surface 18 of the Thus the discharge differential piston valve 14, and opening the same. Via the overflow chamber 19 of the differential piston valve 14 the control fluid passes almost unimpeded into the pressureless return pipe 13 and from there into the control fluid reservoir 15. During the final stage of the valve closing motion the control edge of the receding working piston 6 closes the outlet 10 of the drain 9 so that the backflowing control fluid is compelled to pass through the by-pass pipe 11 and the throttle 12 installed therein, thereby causing a considerable damping effect in this phase of the piston motion and consequently, allowing the injectiongas valve 7 to settle down slowly. As soon as the latter is closed, the working piston 6 has reached its initial position and the differential piston valve 14 returns to its closing position. To ensure positive closing of the differential piston valve 14, a pressure spring 17 acting on the piston front surface 16 in closing direction is provided.

The control pump 1 is then fed for the next delivery pulse via suction pipe 20 from the control fluid reservoir 15. The 'capacity of the control fluid reservoir 15 is such as to make sure that the rise of temperature of the control fluid in operation will not exceed a certain limit. If necessary, a recooling system for the control fluid can be incorporated in the control circuit.

I claim:

A hydraulic control for the operation of the injectiongas valves of international combustion engines, in particular for gas engines, comprising a control pump driven by the internal combustion engine and including individual pump elements for the intermittent pressurization of a control fluid for the feeding of said control pump, a relief valve located at the outlet of each pump element, a jack for each pump element with a laterally discharging drain, a working piston in said jack co-operating with the said injection-gas valve for the purpose of opening and closing the same, a delivery pipe connecting the said pump elements with the said jacks, a check valve installed in each of the said delivery pipes, a drain valve located between the said lateral drain of said jack and the said delivery pipe, said drain valve comprising a differential piston presenting two front surfaces of different sizes, the larger front surface being spring-loaded and impinged upon by the control fluid in the delivery pipe, whereas the smaller front surface is designed as a valve for the said drain, and a by-pass pipe connecting the said drain with the delivery pipe between the jack and the check valve, and a throttle installed in the said by-pass'pipe.

References Cited by the Examiner UNITED STATES PATENTS 2,002,196 5/1935 U cko. 2,011,864 8/1935 Lundh. 2,763,249 9/1956 Flynn.

KARL I. ALBRECHT, Primary Examiner. 

